java replaceAll()

Question

What is the regular expression for replaceAll() function to replace "N/A" with "0" ?

input : N/A
output : 0

Answer 1

Assuming s is a String.

s.replaceAll("N/A", "0");

You don't even need regular expressions for that. This will suffice:

s.replace("N/A", "0");

Answer 2

Why use a regular expression at all? If you don't need a pattern, just use replace:

String output = input.replace("N/A", "0");

• SteveT: The Java API describes the first argument as a regular expression. Hence the form of the question.
• Jon Skeet: @SteveT: Yes, but my point is that there's no need to use replaceAll at all.
• SteveT: Ah - thanks. I didn't notice the different method you suggested. That's good to know.

Answer 3

You can try a faster code. If the string contains only N/A:

return str.equals("N/A") ? "0" : str;

if string contains multiple N/A:

return join(string.split("N/A"), "0")
 + (string.endsWith("N/A") ? "0" : "");

where join() is method:

private String join(String[] split, String string) {
 StringBuffer s = new StringBuffer();
 boolean isNotFirst = false;
 for (String str : split) {
 if (isNotFirst) {
 s.append(string);
 } else {
 isNotFirst = true;
 }
 s.append(str);
 }
 return s.toString();
}

it is twice as fast

• Nayuki: I will assume your code works correctly, but what makes you think that calling split() plus join() is faster than replace() or regex?
• Koss: I tested on large data sets. Unfortunately the test was lost. I think that you can make a new test in the new version of Java. It will be interesting to see the result. I will be glad to help you.